PLANT LICE. 193 
fall is, if anything more serious than either of the others, espe- 
cially if the land be poor and the weather be dry. So far as 
my own observations go, it is more detrimental to the wheat than 
to the apple. The occurrence of the eggs on the twigs of apple, 
during winter, and the appearance of the young on tthe first 
tender buds, and leaves in the spring, are familiar to all horticul- 
turists. I have several times made the attempt to colonize the 
species on wheat plants, with individuals taken from the apple, 
but was never able to thoroughly succeed in this until this year, 
when a series of experiments was begun in the insectary which 
swept away any previous doubts on the subject of migration. 
“Several years ago, on April 17th, all stages of A. mali were 
found on the young buds of quince—a new food plant so far 
as published record goes—and being unrecognizable without the 
winged adults, the attempt was made to carry them on artificially 
until these would appear. In doing this a number escaped from 
the breeding cage where they were kept, and took up their abode 
on some young wheat growing in a box on the same table. Not 
knowing with what generation I began investigating it on the 
quince, it is of course impossible to say whether, as with the Hop 
Aphis, it is not until the third brood is reached that adults at- 
tempt to escape to other plants, and if it was to this third brood 
to which the escaped individuals belonged. It will be only safe to 
say that they were winged and migrated. A wingless female 
from the quince also strayed from the cage and stationed herself 
on some of these wheat plants, and produced a number of young, 
but these all died and fell from the plants. At the same time, 
in a large cage out of doors, others of this species were being 
reared from the eggs on twigs of apple. Wheat was sown 
within this cage, and some of the winged adults, after leaving 
the young buds and leaves, went first to the muslin sides of the 
cage, and afterwards to the wheat plants. One of these remained 
for two weeks alive, on one of the plants, but I could not see 
that she produced young. While these transitions were certainly 
made between the tree and grain plants, nature apparently chose 
to accomplish it only by her own methods, and would brook 
no interference of human assistance. 
“Early in March of the present year, 1893, I placed in the 
insectary a couple of small seedling apple trees, and to these 
bound twigs from the orchard, thickly stuck with eggs of this 
